Datasheet

AD7176-2 Data Sheet
Rev. A | Page 42 of 68
ERROR FLAGS
The status register contains three error bits—ADC_ERROR,
CRC_ERROR, and REG_ERROR—that flag errors with the
ADC conversion, errors with the CRC check, and errors due to
changes in the registers, respectively. In addition, the
ERROR
pin can indicate that an error has occurred.
ADC_ERROR
The ADC_ERROR bit in the status register flags any errors that
occur during the conversion process. The flag is set when an over-
voltage or undervoltage occurs on the analog inputs. The ADC
also outputs all 0s or all 1s when an undervoltage or overvoltage
occurs. This flag is reset only when the overvoltage/undervoltage is
removed. It is not reset by a read of the data register.
CRC_ERROR
If the CRC value that accompanies a write operation does not
correspond with the information sent, the CRC_ERROR flag is
set. The flag is reset as soon as the status register is explicitly read.
REG_ERROR
This flag is used in conjunction with the REG_CHECK bit in
the interface mode register. When the REG_CHECK bit is set,
the AD7176-2 monitors the values in the on-chip registers. If a
bit changes, the REG_ERROR bit is set. Therefore, for writes to
the on-chip registers, REG_CHECK should be set to 0. When
the registers have been updated, the REF_CHK bit can be set to 1.
The AD7176-2 calculates a checksum of the on-chip registers. If
one of the register values has changed, the REG_ERROR bit is
set. If an error is flagged, the REG_CHECK bit must be set to 0
to clear the REG_ERROR bit in the status register. The register
check function does not monitor the data register, status
register, or interface mode register.
ERROR
Pin
When the SYNC_EN bit in the GPIOCON register is set to 1
and Bit ALT_SYNC in the interface mode register is set to 0, the
SYNC
/
ERROR
pin functions as an error input/output pin or a
general-purpose output pin. The ERR_EN bits in the GPIOCON
register determine the function of the pin.
With ERR_EN bits are set to 10, the pin functions as an open-
drain error output pin. The three error bits in the status register
(ADC_ERROR, CRC_ERROR, and REG_ERROR) are OR’ed,
inverted, and mapped to the
ERROR
pin. Therefore, the
ERROR
pin indicates that an error has occurred. The status
register must be read to identify the error source.
When ERR_EN bits are set to 01, the
ERROR
pin functions as
an error input pin. The error pin of another component can be
connected to the AD7176-2
ERROR
pin so that the AD7176-2
indicates when an error occurs on either itself or the external
component. The value on the
ERROR
pin is inverted and OR’ed
with the errors from the ADC conversion, and the result is
indicated via the ADC_ERROR bit in the status register. The value
of the
ERROR
pin is reflected in the ERR_DAT bit in the status
register.
The
ERROR
pin is disabled when the ERR_EN bits are set to 00.
When the ERR_EN1 bits are set to 11, the
ERROR
pin operates
as a general-purpose output.
DATA_STAT
The contents of the status register can be appended to each con-
version on the AD7176-2. This is a useful function if several
channels are enabled. Each time a conversion is output, the
contents of the status register are appended. The two LSBs of
the status register indicate to which channel the conversion
corresponds. In addition, the user can determine if any errors
are being flagged by the error bits.
IOSTRENGTH
The serial interface can operate with a power supply as low as
2 V. However, at this low voltage, the DOUT/
RDY
pin may not
have sufficient drive strength if there is moderate parasitic
capacitance on the board or the SCLK frequency is high. The
IOSTRENGTH bit in the interface mode register increases the
drive strength of the DOUT/
RDY
pin.